In recent years, light-emitting diode (LED) is widely applied and plays an increasingly important role in various fields like display system, lighting system and automobile tail light.
FIG. 1 shows an existing AlGaInP-based LED chip structure, which increases luminance by changing the light-absorbing GaAs substrate into a Si substrate with a mirror system via bonding technology. However, the electrode needs to form ohmic contact with the epitaxial semiconductor and achieves current spreading through the electrode spreading finger, which shields light-emitting and reduces photoelectric efficiency. Later, it is proposed using ITO conduction to replace the metal spreading finger structure, the design of which, however, faces numerous restrictions due to limited number of semiconductor materials available for ohmic contact with ITO.
FIG. 2 shows another existing LED chip structure, in which, the surface spreading finger is replaced by an embedded metal channel structure. The current flows to the n-type semiconductor layer 3 from the top electrode 7, and is horizontally conducted through electron drift of semiconductor materials, to connect the active layer 1 and the p-type semiconductor layer 2. Next, a circuit is completed through conduction between the metal material 5 and the bottom electrode 6, wherein, a dielectric layer 4 isolates the active layer 1 and the metal material 5.